Product novelty 07. March 2024

Hegewald & Peschke offers a clamping system with a modular toolkit for standard-compliant testing of bolts to ISO 898. Suitable specimen grips are inserted into a fixture specially developed for screw testing. This enables quick and easy specimen clamping and prevents the application of transverse forces to the bolt. The specimen grips are adapted to specific bolt sizes and for carrying out different types of tests, such as angular tensile tests. This ensures that the complete range of bolts can be tested with one fixture: from very short to very long bolts with large threads - from machined bolts to finished shoulder head bolts, nuts and even complete sets - from standard thread to fine thread bolts.
Another challenge when testing screws in accordance with DIN EN ISO 898 is determining special characteristic values such as the elongation at break Af and the 0.0048 d yield strength of entire screws. For this purpose, a clip-on extensometer is used in the testing system, which measures the elongation over the entire length of the screw. To do this, the tactile strain gauge is applied to the screw from above and below in specially designed openings in the specimen holder and in the clamping fixture. All parameters for carrying out the tensile test are set in the LabMaster material testing software in accordance with ISO 6892-1. During the test, the control system of the testing machine regulates the test speed in accordance with the specifications of ISO 898-1 - including speed changeover when the 0.0048 d proof stress Fpf is reached. The resulting force-displacement curves and the characteristic values are then automatically determined and displayed in the testing software.